The present invention relates generally to electrical connectors, and, more particularly, to keying systems for electrical connectors.
Electrical connectors are frequently provided with keying means to permit particular pairs of connectors to properly mate and to prevent the mating of connectors which are not intended to be mated. Keying means are especially useful when a plurality of identical connectors are positioned in close proximity to one another, for example, on a printed circuit board. The incorrect matching of complementary connectors to the connectors on the board can cause serious damage to the circuits improperly connected thereby; and the keying means, by ensuring that each complementary connector will mate with only the correct one of the plurality of connectors on the board, minimizes the risk of improper connection. Keying means are particularly important when the connections are made by untrained personnel as the risk of improper connection is especially great in such circumstances.
In one known type of keying system, one of a pair of complementary connectors is provided with a plurality of projections and the other of the pair of connectors is provided with a plurality of recesses or cavities. As the connectors are mated, the projections extend into and are received within the recesses allowing the connectors to properly mate. If the projections and recesses are not correctly aligned with respect to one another, however, proper mating will not occur.
Such keying systems are often not fully satisfactory. Frequently, the keying systems require that the connectors themselves be oriented with respect to one another in a particular way to operate properly. Also, the keying systems are often not effective in preventing mating of a keyed connector with an unkeyed connector.
In another known type of keying system, a key member is secured in one of a pair of complementary connectors and is adapted to cooperate with an opposing key member secured in the other of the pair of connectors. Each key member is secured in its connector in a selected orientation with respect to its opposing key member so that when the connectors are intended to be mated, extended keying portions on the key members pass by each other during mating to allow the connectors to properly mate. If one of the key members is secured in an incorrect orientation with respect to its opposing key member, however, the extended keying portions on the key members will abut one another during mating to prevent proper mating of the connectors.
The key members typically include a portion having a polygonal cross-section and are secured within passageways in the connectors having similar cross-sections. The number of sides of the polygonal shape determines the number of possible orientations of the key members.
Many known polygonal keying systems are also not fully satisfactory. For example, in connectors containing multiple contacts, many such keying systems are capable of preventing incorrectly matched connectors from completely mating with one another, but are not effective in preventing one or more of the individual contacts within the connectors from mating. In many applications, the improper mating of even one pair of contacts in incorrectly matched connectors can close a circuit and cause damage to the circuit.
Also, polygonal keying systems are usually limited in the number of keying combinations they can provide. Most polygonal keying systems include keys having a portion of hexagonal cross-section providing six keying orientations. Although, in theory, the number of keying combinations can be increased by increasing the number of sides of the polygonal portion, in practice, orienting and positioning of keys having more than about six keying orientations becomes quite difficult, particularly in small connectors wherein the key members are also quite small and rather difficult to handle.